1. Field of the Invention
The present invention is generally related to a mechanical fuel pump which can be coupled with a flexible shaft and, more particularly, to a mechanical fuel pump that pressurizes a flow of fuel through the exertion of a spring which causes a piston to move in an axial pumping direction.
2. Description of the Related Art
Those skilled in the art of fuel pumps are familiar with many different types of mechanical fuel pumps and, in particular, with mechanical fuel pumps that comprise a reciprocating piston contained within a generally cylindrical opening of a housing structure. Those skilled in the art of flexible shafts are familiar with many applications in which torque is transmitted through a flexible shaft which comprises a rotatable wire enclosed within a sheath or tube. Those skilled in the art of fuel systems for internal combustion engines are also familiar with the problem associated with vapor lock caused by excessive heat in the environment surrounding fuel handling components.
U.S. Pat. No. 1,575,256, which issued to Del Rio on Mar. 2, 1926, describes an attachment for a suction sweeper. It relates to an improvement in suction sweepers for driving a fan or its equivalent by means of which a powerful suction or partial vacuum is obtained and utilized in removing dust and like particles or fragments of matter from surfaces. It further extends the scope of usefulness of these types of apparatus by the utilization of the motor for a wide range of domestic purposes and without in any way or manner interfering with the usual and customary purpose.
U.S. Pat. No. 4,140,444, which issued to Allen on Feb. 20, 1979, describes a flexible shaft assembly for a progressing cavity pump. The pump components include a tubular stator with an interior helical surface and a hollow tubular orbital rotor within the stator operably connected to the shaft and having an exterior helical surface. The rotor and stator define therebetween sealed pumping cavities that advance axially as the rotor rotates and orbits within the stator. A coupling shaft flexes to accommodate orbital movement of the rotor during operation of the pump. The rotor is coupled to the rotor drive shaft by the flexible coupling shaft that extends through the hollow rotor.
U.S. Pat. No. 4,273,520, which issued to Sutliff et al. on Jun. 16, 1981, describes a deep well pump. A pump barrel open at its lower end is coupled at its upper end by a tubular adapter assembly to the lower end of a pump tubing string.
U.S. Pat. No. 4,597,371, which issued to Wissmann et al. on Jul. 1, 1986, describes a fuel injection apparatus for two stroke engines. It provides for the valve-controlled input of fuel into a pressure chamber of a housing and includes a spring loaded pump piston journaled for reciprocatory movement in a bore to supply the fuel. The pump piston is sealed by an annular seal. For fuel induction, the pump piston has a passageway opening into the pressure chamber and a valve seat. The valve seat of the pump piston operates with a substantially free-flying sealing body for opening and closing the valve.
U.S. Pat. No. 4,701,082, which issued to Fumey on Oct. 20, 1987, describes a multipurpose machining unit. In the multipurpose machining unit with pneumatic spindle feed, driving is performed, starting from a motor unit, directly or via a flexible shaft. An interchangeable gear set makes it possible to select the number of revolutions of the tool in accordance with its purpose.
U.S. Pat. No. 4,936,492, which issued to Amiel et al. on Jun. 26, 1990, describes a precompression pump. It comprises an open ended hollow body defining a pump chamber and an inlet orifice which communicates with a reservoir. The pump body has four side walls. A piston is mounted for reciprocal movement through a portion of the body and it extends through the upper end of the body. A ferrule is disposed above the body and defines an aperture through which the piston extends. A seal is disposed between the ferrule and the body, and the seal surrounds a portion of the piston. A spring is mounted in the body and the spring actively biases the piston toward the top of the body.
U.S. Pat. No. 5,025,559, which issued to McCullough on Jun. 25, 1991, describes a pneumatic control system for a meat trimming knife. A diaphragm mounted in the handle of the knife is compressed by the manual movement of a piston by an operator. The diaphragm is connected to a pressure switch which senses compression of the diaphragm and generates an electric control signal which actuates an electric clutch which couples the output shaft of the electric motor to the flexible cable for rotating the cutting blade.
U.S. Pat. No. 5,085,564, which issued to Naylor et al. on Feb. 4, 1992, describes a flexible drive shaft. The shaft for a helical gear pump has a rotor in which the drive shaft is formed with an enlarged head and is provided with a plastic material coating. The drive shaft is held onto the rotor by bolts passing through holes in the head and apertures in a cap.
U.S. Pat. No. 5,370,507, which issued to Dunn et al. on Dec. 6, 1994, describes a reciprocating chemical pump. All parts wetted by the fluid being pumped are made of flouroplastic material with the pumps having check valves that include floating ball members and O-rings positioned adjacent to the floating ball members. The retaining area in which the O-ring is received has a diameter that is at least about 0.01 inch larger than the diameter of the O-ring so as to allow the O-ring to move slightly.
U.S. Pat. No. 5,374,168, which issued to Kozawa et al. on Dec. 20, 1994, describes a reciprocating piston fluid pump. It comprises a pump driving section including a cam operated by an engine and a roller driven by the cam, the roller being provided at a lower end of a piston rod. It also comprises a piston provided at an upper portion of the piston rod and a pump chamber housing the piston and divided into a piston upper chamber and a piston lower chamber by the piston. The pump chamber includes a bearing opening at a central portion of the piston lower chamber through which the piston rod extends. A rod seal retainer portion is provided between the piston rod and the bearing opening of the pump chamber. A spring for urging the piston rod downwardly is provided. An oil passage for communicating the pump upper chamber of the pump lower chamber with the bearing opening is provided and the oil passage is provided on an oil seal member of the piston rod.
U.S. Pat. No. 5,494,015, which issued to Rynhart on Feb. 27, 1996, describes a fuel injector assembly. The injector assembly has a body with a bore having a gas passage at one end for communication with an engine combustion chamber. A piston is slidable in the bore. A fuel pump is mounted within the body having a plunger which is mounted on the piston for reciprocal pumping movement within a complimentary fuel pump cylinder for delivery of fuel to a nozzle assembly. The nozzle assembly is mounted on the piston and projects through the gas passage. The piston is urged downwardly by a timing spring so that a valve head on the nozzle assembly engages a valve seat until the pressure of combustion chamber gases acting on the outer portion of the nozzle is sufficient to overcome spring pressure and move the piston upwardly opening the passage to the piston so that the gases snap the piston upwardly due to the increased area exposed to the gases.
U.S. Pat. No. 5,810,570, which issued to Nguyen on Sep. 22, 1998, describes a super-low net positive suction head cryogenic reciprocating pump. The pump has a spring loaded intake valve made of magnetic material and a reciprocating piston having a permanent magnet at its head end. The intake valve is positioned such that when the piston is at or near the top of its stroke, the magnet will tend to pull the intake valve into an open position. The pump also preferably includes a mechanical spring energized seal at the upper end of the piston.
U.S. Pat. No. 5,996,472, which issued to Nguyen et al. on Dec. 7, 1999, describes a cryogenic reciprocating pump. The pump has a cylinder sleeve, head, intake valve, discharge valve, and a reciprocating piston including a mechanical spring energized seal having a generally U-shaped jacket and a helical spring in the bight of the U.
U.S. Pat. No. 5,924,929, which issued to Silver on Jul. 20, 1999, describes a flexible driveshaft and driveshaft and rotor assembly. The driveshaft, provided with a coating, is formed of titanium or similar metal. A relatively inexpensive metal flanged head portion is fastened to an end portion of the driveshaft and is bolted to the rotor. The structure enables a relatively short driveshaft to be used which is capable of transmitting heavy torque.
U.S. Pat. No. 6,499,974, which issued to Bach on Dec. 31, 2002, describes a piston pump. The pump has a piston axially movable against the force of the spring within an operating chamber connected via check valves to an operating cylinder and a hydraulic medium supply. A section of the piston that extends into the operating chamber has a reduced diameter extension which extends from a shoulder of the piston that delimits the operating chamber. The extension includes a thickened free end having a sealing surface facing the shoulder. A valve disk is located and guided on the extension of a gap between the shoulder and sealing surface and is capable of axially reciprocating movements thereon. The valve disk is provided with openings which provide a passageway for hydraulic medium from the operating chamber to a second check valve. The openings are blocked when the valve disk abuts the sealing surface.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a fuel pump could be configured so as to avoid a reduction of pressure of liquid fuel that is sufficient to cause the liquid fuel to vaporize or boil, particularly under elevated temperature conditions. It would also be significantly beneficial if a fuel pump could be developed which is simple in construction and yet able to consistently provide pressurized fuel at a generally constant pressure magnitude without undue variations in the pressure of the fuel being provided to an internal combustion engine. It would also be significantly beneficial if a fuel pump could be developed which could be mounted at a distance away from its source of motive power in order to allow the fuel pump to be spaced apart from heat sources that would otherwise exacerbate problems related to fuel vaporization and boiling.